Channel 4 chief executive David Abraham has said the broadcaster "pulled off an unbelievable balancing act" in 2011 despite its main network dropping to its lowest share of the audience since the mid-1980s.

The flagship Channel 4 network had a 6.8% share of the audience in 2011, falling to 5.9% without its timeshifted offering, Channel 4 +1. This was down from 7% in 2010 and its lowest since 1984, when it had a 6% share (including Welsh-language channel, S4C).

Abraham said the core channel's year-on-year decline was the smallest for five years and it had held up better than its rival terrestrial broadcasters.

Overall audience share for Channel 4's portfolio of services, including E4, More4 and Film4, was up year on year to 11.6%, narrowly below its highest-ever share of 11.9% in 2006.

"It's the lowest amount of decline for five years. Digital switchover has led to terrestrial decline over a prolonged period; Channel 4 has held up much better than other terrestrials," said Abraham.

"We trade on a portfolio of channels and it's the biggest growth of any terrestrial portfolio of channels in 2011.

"Not that we wouldn't want to see Channel 4 being immensely strong – we do – but to experience the lowest level of decline for five years in the first year without Big Brother is an immense achievement.

"Our impact as a set of channels is as great as it ever was under Michael Grade or any other ... but it is spread over multiple platforms."

Abraham said he would like to see Channel 4 (including Channel 4 +1) remain stable at a 6.8% share of the audience, where it has stayed in 2012 to date.

"I think it's unbelievable that public service content in the first year without Big Brother. That's amazing," added Abraham.

"We could have run wall-to-wall lifestyle programming and all you have would have said we'd betrayed the remit but we've delivered the remit and we've grown the portfolio. That's an unbelievable balancing act to pull off."

Channel 4 unveiled a new programming on Monday including a season of programmes about mental health, 4 Goes Mad, and Hotel Britannia, the "ultimate hotel" which will be run for a week by presenters including Gordon Ramsay, Mary Portas, Sarah Beeny and Gok Wan.

New dramas will include Here and There, directed by Michael Winterbottom and starring John Simm and Shirley Henderson. Filmed over five years, it tells the story of a family living through a prison sentence.

4 Goes Mad will see eight people with mental health conditions appear "undercover" on some of Channel 4's most popular shows.

Jay Hunt, Channel 4 chief operating officer, said the show would aim to look at prejudices in the workplace. "We are casting people with mental health problems and asking: we gave them a job, would you?"

Answering questions at the launch of the channel's 2011 annual report on Monday, Hunt admitted Channel 4 soap Hollyoaks "was not on its best form", but she "absolutely believed in Hollyoaks as an incredibly important part of what we have on Channel 4 to serve a young audience".

"It is always true with soaps you have ups and downs, at the end of last year it was on stonking form. One slightly dud storyline can dip the viewing figures, that's how it goes. I feel pretty relaxed about it, I am in constant touch with [Hollyoaks producer] Lime."

Hunt said Channel 4's live drug-taking experiment unveiled at last year's annual report was still in the pipeline but had taken longer than expected.

Another long-anticipated Channel 4 show first announced three years ago, in which it will deliberately crash a plane, will air later this year, she added. "Difficult shows take a long time to air," she said.

"My first year has been a period of a lot of change, I think that's stopping now," added Hunt. "I feel we have in place a creative leadership team which has an acute sense of what differentiates Channel 4 from the other broadcasters."

She said the channel remained in discussions with controversial comic Frankie Boyle but they had not yet found the right project.

Hunt said she remained committed to finding new entertainment and comedy formats but admitted there were "some issues with execution" in its recent Micky Flanagan vehicle, The Mad Bad Ad Show.

"One of the things I felt strongly about when I arrived here was is it really Channel 4 to have Embarrassing Bodies on a Friday night, which is where I started when I got here," she added.

"It's a long haul, standout comedy and big entertainment hits are the hardest things to find, they are market failure genres in lots of ways."

• To contact the MediaGuardian news desk email editor@mediatheguardian.com or phone 020 3353 3857. For all other inquiries please call the main Guardian switchboard on 020 3353 2000. If you are writing a comment for publication, please mark clearly "for publication".

• To get the latest media news to your desktop or mobile, follow MediaGuardian on Twitter and Facebook.